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Researchers from the United Kingdom and the United States conducted the research, recently publishing their results in the scientific journal Molecular Human Reproduction.

Taking ovarian tissue from 10 women in their late 20s and 30s, the scientists activitated the eggs to develop from their earliest stage to maturity, using different cocktails of nutrients. In total, 48 eggs reached the second to the last stage of maturity and nine reached full maturity.

"It's very exciting to obtain proof of principle that it's possible to reach this stage in human tissue," Dr. Evelyn Telfer, one of the researchers, told the BBC, discussing the results.

However, Telfer cautioned that much more research needs to be conducted before the technique could be used by fertilization clinics. Widespread implementation of the procedure could still be years away.

"But that has to be tempered by the whole lot of work needed to improve the culture conditions and test the quality of the oocytes [eggs]," she said.

"Apart from any clinical applications, this is a big breakthrough in improving understanding of human egg development."

The process would make it much easier for women to undergo in vitro fertilization (IVF), if developed fully, The Telegraph reported. They would simply have a small tissue biopsy, instead of distressing rounds of hormone-triggered ovulation.

Experts also suggest the breakthrough could lead to new approaches to fertility preservation for women at risk of premature fertility loss, such as those undergoing radiotherapy or chemotherapy. Young girls who have not yet gone through puberty could even preserve and freeze their ovarian tissue for future implantation.

At the same time, some scientists caution that the approach could have drawbacks for those with cancer.

"The big worry, and the big risk, is can you put cancer cells back," Dr. Stuart Lavery, a consultant gynecologist at Hammersmith Hospital, who was not involved with the study, told The Guardian.

At the same time, Telfer pointed out that it could be the only option for young girls who hope to get pregnant later in life after beating cancer.

"[For young girls] that is the only option they have to preserve their fertility." she said.

This new method could also dramatically increase the viable number of eggs that could be harvested from an individual woman about to undergo chemo.

With current techniques, patients must "go through the quick cycle of IVF before their chemo, so it can sometimes delay things, and also you may only get 15 eggs or so; because IVF is so inefficient, only having 10 or 15 eggs is not going to guarantee them a baby," Lavery explained.

"With this [new] procedure, you could potentially get thousands or hundreds of eggs," he said.

In the past, scientists have only managed to achieve partial growth of the human egg cells in a lab. The new study is groundbreaking in that the same human eggs were brought from their very earliest stages of development to the point when they would be released from the ovaries, ready for fertilization.

However, even as scientists are hailing the breakthrough, they also recognize potential problems and drawbacks.

The lab grown eggs reached maturity in just 22 days, while the process takes five months in the body. This makes it unclear whether they can readily combine with sperm to make a healthy embryo. Telfer thinks the quicker growth may simply be due to many inhibitory signals from the body being absent, but more research is needed to determine exactly.

"Significant further research is now needed to confirm that these eggs are healthy and functioning as they should do," Dr. Helen Picton, an expert in reproduction and early development from the University of Leeds, said.

Despite the remaining questions and need for further study, experts are hailing the results as "extraordinarily important."

"It has real potential for application," Kyle Orwig, a stem cell biologist at the Magee-Womens Research Institute at the University of Pittsburgh in Pennsylvania, who was not involved with the study, told Science Magazine.